摘要:

A study was made of the number of plastids and mitochondria present in generative cells ofSolanumimmediately after microspore mitosis, and the fate of these organelles during development of the pollen was determined. Changes were followed via electron microscopy of anthers ofS. chacoenseandS. tuberosumGroup Phureja ×S. chacoense.In earliest stages the generative cells were oval and had one surface along the intine and other surfaces in contact with the vegetative cell. As the pollen matured the generative cells elongated, became spindle‐shaped, and were completely engulfed in the vegetative cells. At the earliest stages studied, both mitochondria and plastids were present in the generative cell. Plastids of the generative cell were, in contrast to those of the vegetative cells, fewer, smaller, and lacking in starch. Through the maturation stages the content of these organelles in the vegetative cells remained unchanged. While the generative cells retained mitochondria until anthesis, their plastids disappeared completely during maturation. This selective loss during generative cell maturation could lead to transmission of those characteristics encoded in plastid DNA through the pistillate parent only. The mechanism could explain earlier genetic evidence that plastid characters ofSolanumwere transmitted uniparentally.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb12359.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

An electron microscope study was made of the central cell and the development of the free nuclear endosperm surrounding the zygote and synergids during the first three days after pollination. The cytoplasm of the central cell, concentrated around the partially‐fused polar nuclei, contains many ribosomes, mitochondria and large, dense, starch‐containing plastids, some dictyosomes and lipid bodies, and long, single cisternae of rough endoplasmic reticulum (RER) that frequently terminate in whorls. Dense, core‐containing microbodies are closely associated with the RER. After fertilization the cytoplasm of the 2‐and 4‐nucleate endosperm shows an increase in number of dictyosomes, and in amount of RER which becomes stacked in arrays of parallel cisternae. Cup‐shaped plastids are associated with many long, helical polysomes. Perinuclear aggregates of dense, granular material also appear after fertilization. Granular aggregates and helical polysomes disappear after the first few divisions of the primary endosperm nucleus. During the second and third days of development there is an increase in dictyosome number and RER proliferation, and endosperm nuclei become deeply lobed. Concurrently, there is a sharp decline in the starch and lipid reserves of the central cell and elaborate transfer walls are formed at the micropylar end of the embryo sac and on the outer surface of the degenerating synergid. The transfer walls contain groups of small, membrane‐bound vesicles, and are associated with large numbers of mitochondria and with the smooth endoplasmic reticulum.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb12360.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

After Jacobs’ recent discovery of almost absolute basipetal polarity of IAA‐14C movement through young internodes ofColeus, tracheary regeneration around a wound in the stem was re‐investigated to see if it showed parallel changes from the less strict polarity of IAA‐14C described decades ago. As determined from either counts of “complete regenerated strands” or from finer details of regeneration, tracheary regeneration was very strongly polar. If leaves were present only below the wound, no regenerated strands developed unless there was a sizeable length of leafless stem remaining above the wound. If there were leaves below the wound as well as above it the amount of regeneration was usually reduced. The short strands of acropetally regenerating tracheary cells, previously interpreted as resulting from acropetal IAA movement, were observed in plants with leaves above but not below the wound, and were not seen in plants with leaves only below the wound. Hence, they are more likely to result from basipetally moving IAA. Isolated patches of tracheary regeneration were observed under several conditions. The wound interfered with development of the leaf directly above the wound.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb12361.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

The increase in [14C]‐2‐deoxy‐D‐glucose uptake by leaf discs 24 hr after fumigation was used as a measure of ozone injury to pinto bean leaves (Phaseolus vulgaris). This method showed that the primary leaves were most affected by ozone when plants were 10 to 12 days old, which coincided with the time of maximum leaf necrosis. However, 8‐day‐old plants, which had no visible leaf injury, still showed a higher uptake rate than controls, indicating that injury occurred at the cellular level. In these younger plants, uptake was shown to return to normal over a 5 day period. Moreover, the rate of this “repair” was retarded by cold or continuous darkness, enhanced by continuous light, and very markedly increased by glucose applied to the leaves. The timing of the glucose application was not critical, nor did H2O or mannitol have an effect. The results suggest that ozone injury at the cellular level can be repaired by energy‐dependent processes so that necrosis of the leaf tissue does not occur. These experiments also show that conditions and treatments after ozone exposure can alter the degree of ozone injury.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb12362.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

Analyses were made, by study of reciprocal crosses, of cytoplasmic factors ofSolanum tuberosumssp.andigenaandS. tuberosumssp.tuberosumincluding both northern hemipshere cultivated clones and clones from Chiloe Archipelago in Coastal Chile. The purpose was to compare the cytoplasmic factors of these three sorts ofS. tuberosumwith those of their diploid ancestors and with one another as aids in determining their positions on pathways of evolutionary descent. Preliminary to making the comparisons it was shown that the cytoplasm‐chromosomal gene interaction that produces deformed flowers in diploid forms ofSolanumfunctions also in induced autotetraploids, with deformed flowers being expressed in [df8]‐dfdfdfdfindividuals. Plants of theS. stenotomum‐phurejacomplex, putative ancestors ofS. tuberosumssp.andigena, were known from earlier work to have the [df8] plasmon factor, but ssp.andigenaitself was found to lack it. A newly discovered cytoplasmic abnormality, anther‐lobe overlap, is expressed in plants having plasmon factor [lo8] and homozygous for recessive alleleslo.The [lo8] plasmon factor is present inS. phurejaand inS. tuberosumssp.andigena.Altogether, ssp.andigenapotatoes match their putativestenotomum‐phurejaancestors in eight of the nine plasmon factors identified to date, differing with them only in the lack of [df8]. Northern hemisphere and Chiloe clones ofS. tuberosumssp.tuberosumlack the [df8] and the [lo8] plasmon factors. Chiloe clones are identical to northern hemisphere cultivated ones in all eight plasmon factors for which they were tested. Both contrasted with ssp.andigena, their putative ancestor, in eight of nine factors tested, resembling it only in their common lack of [df8]. The evidence supports the idea that clones cultivated now in the northern hemisphere are descendants of direct imports from coastal Chile. The clone Rough Purple Chili was an example of an imported clone that became important in potato breeding, but it has not been clear whether it was brought from Chile or from Andean regions of northern South America. The leaf form and cytoplasmic factors of Garnet Chili, a first generation derivative of Rough Purple Chili, were found to be those ofS. tuberosumssp.tuberosum.Rough Purple Chili is, therefore, an example of such direct importation from Chile.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb12363.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

Roots ofEquisetum hyemaleL. var.affine(Engelm.) A. A. Eat. were fixed in glutaraldehyde, postfixed in osmium tetroxide, and sieve elements of various ages were examined with the electron microscope. Young sieve elements are distinguished by their position within the vascular cylinder and by the presence of numerous refractive spherules, which originate within dilated portions of the endoplasmic reticulum (ER). Early in development, the sieve‐element walls undergo a substantial increase in thickness. This is followed by the appearance of massive ER aggregates in the cytoplasm and then by a phase involving stacking and sequestering of the remaining ER. Nuclear degeneration is initiated shortly after the appearance of the ER aggregates. The chromatin condenses into masses of variable size along the inner surface of the nuclear envelope. The envelope then ruptures and chromatin is released into the cytoplasm. During the period of nuclear degeneration, mitochondria and plastids undergo structural modification, while components such as dictyosomes, microtubules, and ribosomes degenerate and disappear. The remaining cytoplasmic components assume a parietal position in the cell, leaving the lumen of the cell clear in appearance. At maturity, the plasmalemma‐lined sieve element contains plastids, mitochondria, some ER, and refractive spherules. At this time many of the refractive spherules are discharged into the region of the wall. Pores between sieve elements occur largely on the end walls. During pore development, tubules of ER apparently traverse the pores, but because of the presence of massive callose deposits in the material examined, the true condition of mature pores could not be determined. The connections between mature sieve elements and pericycle cells are characterized by the presence of massive wall thickenings on the pericycle‐cell side. Plasmodesmata in the wall thickening are matched by pores on the sieve‐element side. Ontogenetic and cytoplasmic factors argue against use of the term “companion cell” for the vascular parenchyma cells associated with the sieve elements.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb12364.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

Experimental hybrids involving the three diploid subspecies ofEpilobiumsect.Zauschneriaformed 15 bivalents at meiotic metaphase I, as did experimental hybrids between the three other species ofEpilobium(comprising sect.Cordylophorum) withn= 15. The gametic chromosome number ofE. suffruticosumNutt.,n= 15, and its relationship to the other two species are reported for the first time. Although we have not obtained hybrids between the species of these two sections, their morphological similarities are impressive and they are surely closely related.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb12365.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

Whereas a medium containing kinetin alone enabled a fewDianthus caryophyllusL. apical meristem dome explants to develop into rooted plants, the highest frequency of plants was obtained in one containing supplements of both IAA and kinetin. In an unsupplemented medium, continued development required that explants have 2 pairs of primordial and a pair of expanding leaves. Kinetin alone caused production of many new leaves, but the development was significantly less than when it was furnished in combination with IAA. IAA given alone caused meristem explants to develop primarily callus, roots, and a few leaves. Gibberellin and abscisic acid were without promotive effects on leaf and shoot formation. A balance of hormonal substances, synthesized in young leaf structures and relocated to the meristem, is proposed as the fundamental mechanism that regulates new leaf initiation in the shoot apex.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb12366.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

The elongating, tip cell of the protonema ofDawsonia superbais characterized by a variety of organelles distributed uniformly over the length of the cell. Chloroplasts, vacuoles, mitochondria and dictyosomes are present in the terminal portion of the cell. Dictyosomes are abundant throughout the cell and their production of vesicles is pronounced. Stratification of the cytoplasm and exclusion of organelles from the tip are not observed. The orientation of microtubules and microfibrils follows the pattern observed in filamentous fern prothallia. Microtubules are not observed at the tip of the protonema, but microfibrils are abundant and randomly oriented. While microtubules and microfibrils in lower regions of the apical dome are arranged randomly, more basally they assume an axial arrangement.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb12367.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

Cells in mature embryos and stationary phase (SP) root meristems of pea arrest in G1 and G2 of the cell cycle. The patterns of distribution of G2 nuclei in radicles and SP meristems, with and without G2 factor, were compared by using cytophotometric analysis of the relative amount of DNA/nucleus in sectioned material. Radicles and SP meristems were each divided into 5 zones and the ratio of G1 to G2 nuclei was determined for each zone. The G2 population in the radicle is restricted mainly to the embryonic cortex. A small part of the G2 population was located in the central cylinder and the root cap. In SP meristems without G2 factor, the pattern of distribution of G2 cells was similar to that in radicles. SP meristems with G2 factor contained G2 arrested nuclei in all regions of the root tip. In each region the percentage of G2 nuclei was higher than that in the same region of SP meristems without G2 factor. This indicates that the population of cells that responds to G2 factor is distributed throughout the root tip.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb12368.x

出版商:Wiley    

年代:1977

数据来源: WILEY